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PUSHING THE OPERATIONAL LIMITS OF SURFACE SEALS AND ITS
EFFECT ON CURRENT MATERIALS SPECIFICATIONS
Douglas Judd
BACKGROUND
TRH 3 April 2007 is excellent guideline for SELECTION, DESIGN and CONSTRUCTION of Surfacing Seals
COLTO and SADC standards provide for Surfacing Seals under normal conditions.
TRH 3 issues warnings relating to sealing under HIGH TRAFFIC VOLUMES.
HIGH VOLUME roads relates to HEAVY TRUCK TRAFFIC rather than many light vehicle’s.
Equivalent Light Vehicle (ELV) 1 HEAVY = 40+ ELV
BACKGROUND
Low risk option is to assume an upper threshold of 40,000 ELV for SURFACING SEALS.
There are major performance benefits in using SURFACING SEALS on HIGH (HEAVY) VOLUME ROADS
Paper based on experience gained in applying SURFACING SEALS to HIGH VOLUME ROADS in the 50,000 – 80,000 ELV range. Approximately 2 million m2 under traffic
INTRODUCTION
Surfacing Seals in High Volume applications relates to RESEALING not New Construction
In this application SURFACING SEALS compete head to head with UTFC and other asphalt mixes
Trigger for use of SURFACING SEAL is PERFORMANCE and not only ECONOMICS
Interlayers Water proofing “High” deflection Skid Resistance
INTRODUCTION
EXAMPLES
NOTE High SLOW LANE ELV Average to Low FAST LANE ELV
DESIGN ASPECTS
Traffic
Selection of Surfacing Seal Type
Road Geometry
Materials Binder Aggregate
Pre-Treatment Requirements
DESIGN ASPECTS - TRAFFIC
AADT/Lane VS elv for % Heavy
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 5000 10000 15000 20000 25000 30000 35000
AADT / Lane
eq
uiv
ale
nt
ligh
t v
eh
icle
s (
1h
v =
40
elv
)
2%
5%
8%
10%
12%
15%
20%
20000
40000
High Volume
DESIGN ASPECTS – TYPE OF SEALPROPERTIES OF A GOOD SEAL – HIGH VOLUME ROADS
As much binder as possible Good Voids Sufficient Texture Depth Even Ride Quiet Ride
BINDER VOIDSTEXTURE
DEPTHEVEN RIDE
QUIET RIDE
EASY TO CONSTRUCT
DOUBLE SEAL
MOREMORE IN MATRIX
LESS YES MORE LESS
SINGLE SEAL LESSLESS - OPEN
HIGH YES - * LESS YES
DESIGN ASPECTS – ROAD GEOMETRY
Heavier trafficked roads generally HIGHER GEOMETRIC STANDARDS
LANE WIDTH
60% of LANE WIDTH subject to ELV of 20-30% of DESIGN TRAFFIC
DESIGN ASPECTS - BINDER
USE TG1
Performance characteristics required INITIAL ADHESION BINDER LAYER THICKNESS HIGH TEMPERATURE RESISTANCE TO FLOW LOW TEMPERATURE ADHESION / DUCTILITY
MODIFIED BINDERS are recommended
Steer clear of Diluents / Fluxes / Cut-backs
DESIGN ASPECTS - AGGREGATES
Designer has good control over aggregate; TRH 3 Chapter 8 & COLTO 4300 specifications required
modification for high volume application;
Tight control required on: ACV / 10% FACT PSV Grading – do not produce oversize. FI & ALD
Use TRH3 design graphs to determine min ALD required
DESIGN ASPECTS – PRE-TREATMENT
Guidelines in TRH 3 are appropriate
Consider at this stage to apply additional binder outside of wheel path;
Consider special treatment in wheel paths.
CONSTRUCTION ASPECTS
Accommodation of Traffic
Opening road to Traffic
Climatic Conditions
Contractors Equipment
Joints between Sprays
CONSTRUCTION ASPECTS – ACCOMODATION OF TRAFFIC
ACCOMMODATION OF TRAFFIC Ability to deal with traffic influences selection of
Seal Type Can the sealed lane be kept closed for 24 hours?
OPENING TO TRAFFIC Complete Seal open to Traffic for 2 hrs at +25ºC
before temp drops. In hot weather do not open fresh seal if road temp >
SP - 15ºC
CONSTRUCTION ASPECTS – CLIMATIC CONDITIONS
Apply COLTO limitations rigorously. General rule – 1 May - 30 September – SEAL
EMBARGO Abandon work if overnight temps consistently drop
below 8ºC. Avoid sealing into Autumn. Any add-on adjustment
will show next summer.
Recommended best time Early summer to March. (Seal through shut-down?)
CONSTRUCTION ASPECTS – CONTRACTORS EQUIPMENT
Equipment in good working order
Sufficient TRUCKS – cover binder in 5 minutes
Sufficient ROLLERS to complement daily production
Consider STEEL WHEEL ROLLER
SELF PROPELLED BROOMS
CONSTRUCTION ASPECTS – JOINTS AND LOW TRAFFIC AREAS
Longitudinal joint does not have to be on lane line;
Consider thicker joint on Centreline;
Keep away from outside (yellow) edge line;
Do not place two joints on same longitudinal line.
Fogspray outside wheelpaths
CONCLUSIONS
Selection based on PERFORMANCE not Economics;
Consider, IS IT PHYSICALLY POSSIBLE to construct?
Best quality MATERIALS required;
ATTENTION TO DETAIL during construction required to ensure performance;
Apply TRH 3 with PROJECT SPECIFICATION amendments;
PROJECT SPECIFICATIONS REQUIRED
Restrictions with respect to Climatic / Weather Conditions
Aggregate requirements Accommodation of Traffic Opening to Traffic Isolated application of additional binder Joint positions Equipment
Rollers Rotary Brooms
THANK YOU